Question 29.12: Assume that the two-step ADC shown in Fig. 29.26 has four bi......
Assume that the two-step ADC shown in Fig. 29.26 has four bits of resolution. Make a table listing the MSBs, V_{1},\ V_{2},\ V_{3}, and the LSBs for V_{I N} = 2, 4, 9, and 15 V assuming that V_{R E F}=16\ V.
Since V_{R E F} was conveniently made 16 V, each LSB will be 1 V. If V_{I N}=2\ V, the output of the first 2-bit Flash converter will be 00 since V_{R E F}=16\ V and each resistor drops 4 V. The output of the 2-bit DAC, V_{1}, will therefore be 0, resulting in V_{2}=2\ V. The multiplication of V_{2} by the 4 results in V_{3}=8\ V. Remember that each 2-bit Flash converter resembles that of Fig. 29.21. The thermometer code from the second Flash converter will be 0011, which results in 10 as the LSBs. The other values can be calculated as seen in Fig. 29.28.
